Ultra-Strong Aluminum Alloys for High-Temperature Applications

NU 2020-206

INVENTORS
Amir Rezaei Farkoosh
David Dunand*
David Seidman*

SHORT DESCRIPTION
Novel alloys that can function under demanding high temperatures and high stress

ABSTRACT
The best high-temperature commercial aluminum alloys become very weak at temperatures exceeding about 300oC, due to the coarsening or dissolution of their strengthening precipitates. Over the last two decades, new aluminum alloys (Scalmalloy from Airbus and NanoAl from Braidy) have become available that utilize slow-diffusing alloying additions, such as scandium and zirconium, which upon aging form thermally stable Al3(Sc1-xZrx) nanoprecipitates with an L12 structure. Their use, however, is limited to low stress applications at 300-400oC due to the limited strength and creep resistance imparted by the small volume fractions of the L12-nanoprecipitates. They have a high production cost due to the use of Zr, and especially Sc. Northwestern researchers have created and identified a series of low-cost, castable, weldable, brazeable and heat-treatable aluminum alloys developed, based on the modifications made to aluminum-manganese-based (for example, commercial 3000 series) alloys.  These non-heat treatable (that is, with negligible precipitation strengthening) Mn-containing aluminum alloys transform into heat treatable (that is, precipitation strengthened) alloys with high-strength, ductility, thermal stability, creep, coarsening and recrystallization resistance. The resulting alloys can be utilized at high temperatures under high stresses for a variety of light-weight applications.  The significantly higher brazing temperature, when compared to the commercially available aluminum alloys, makes the novel alloys especially well-suited for use in heat exchanger applications in truck and car diesel engine charge-air-coolers as well as other brazed aluminum heat exchangers.  The method used to create these alloy also be applied to increase the recrystallization resistance of wrought aluminum alloys, which would enhance their formability, workability and mechanical properties at ambient and high temperatures, after exposure to very high temperatures.

APPLICATIONS

• Automotive applications- e.g. engine blocks, cylinder heads, pistons, brake rotors
• Aerospace applications- e.g. heat-exchangers or structural parts near engines

ADVANTAGES

• Higher strength and creep resistance at high temperatures
• Retain strength at low temperature with enhanced brazeability and recrystallization resistance
• Compatible with the Al-Si brazing materials without significant alterations in the microstructure and mechanical properties
• More economical production cost

PUBLICATION
Manuscript in preparation

IP STATUS
A provisional application has been filed.